1. Field of the Invention
The invention relates generally to thermally responsive valves and more specifically to a novel thermally activated sleeve valve.
2. Description of the Related Art
Valves that open and close in response to changes in temperature are well known. Typical examples include valves in automotive coolant systems, which open at a predetermined temperature to allow coolant to flow to cooling devices such as radiators. The typical automotive thermostat remains closed until a predetermined temperature and then opens to provide a fluid flow path to the radiator. This form of valve is open or closed and is commonly referred to as a two-way valve. An alternative configuration for a thermostatically controlled valve is that of a diverter, or three-way valve. In a diverter valve, a valve member in a first or xe2x80x9ccoldxe2x80x9d position allows fluid to flow in a first path through the valve. When the fluid reaches a predetermined temperature, the valve actuates to divert fluid flow to a second or xe2x80x9chotxe2x80x9d path through the valve. A three-way thermally activated valve typically includes a fluid inlet, a xe2x80x9ccoldxe2x80x9d flow position outlet and a xe2x80x9chotxe2x80x9d flow position outlet. When a diverter valve is activated to the xe2x80x9chotxe2x80x9d, or divert position, the xe2x80x9ccoldxe2x80x9d flow path is closed. A thermally activated mixing valve has a similar overall configuration to the diverter valve, with the exception that there are xe2x80x9chotxe2x80x9d and xe2x80x9ccoldxe2x80x9d inlets and the valve member is arranged to vary the proportions of fluid from these inlets through the valve to a xe2x80x9cmixedxe2x80x9d temperature controlled outlet.
In a typical sleeve valve arrangement is one in which the valve sleeve reciprocates in a cylindrical valve chamber to cover and uncover ports communicating with the valve chamber at right angles to the valve chamber axis. An inlet or outlet may be in axial alignment with the cylindrical valve chamber. The temperature sensitive actuator and its associated biasing springs and/or adjustment mechanism typically close one end of the valve chamber. Because the actuator and associated hardware block one end of the valve chamber, typical thermally activated valves do not have a fluid flow path aligned with the valve chamber in any position of the valve member.
The Invention is directed to a no leak thermally actuated valve adapted to provide an axial cold flow path through a substantially cylindrical valve chamber between an inlet and a co-axial outlet, and a closed or diverted hot flow path. In a general aspect of the valve, a wax filled actuator is coupled to a valve sleeve to move the sleeve from an open position in which radial flow openings in the sleeve communicate with a portion of the valve chamber to a closed position in which the radial flow openings are closed by a smaller diameter portion of the valve chamber that closely surrounds the sleeve. A flow-through end cap closes the larger diameter end of the valve chamber and provides an axially aligned fixed stop for the actuator piston. The actuator piston remains stationary while the actuator body and coupled valve sleeve float together between the cold (open) and hot (closed or diverted) positions within the valve body.
In a three-way valve, a diverter port communicates with the sleeve radial flow openings when the sleeve is in the closed position, resulting in a diverted fluid flow path. In a two-way valve, the closed position shuts off axial flow through the valve.
A thermally actuated valve exemplary of aspects of the present invention provides an axial flow path through the valve chamber by equipping one end of the valve housing with an end cap that both allows fluid flow and provides a hard stop for the piston of a temperature sensitive actuator. The valve housing defines an axially extending valve chamber in the form of a stepped bore extending between an inlet and an outlet. A smaller diameter portion of the stepped bore adjacent the inlet defines a sleeve chamber. A cylindrical valve sleeve with radial fluid flow openings is coupled to a thermally responsive actuator to form a valve member assembly. A return spring is compressed between an internal rim of the sleeve and the inlet end of the valve housing to bias the valve member assembly toward an open position. An open position corresponds to a sleeve position in which the radial fluid flow openings communicate with the larger diameter portion of the stepped bore adjacent the outlet, allowing fluid flow radially through the openings and axially through the end cap to the outlet. Heating the actuator through its activation temperature range causes the piston to extend from the actuator body against the hard stop and move the valve sleeve into the sleeve chamber against the bias of a return spring to a closed position. A closed position of the thermally actuated valve corresponds to a sleeve position in which the radial fluid flow openings are closed by the inside surface of the sleeve chamber and fluid flow toward the outlet is shut off.
One aspect of the invention relates to a spring-loaded coupling of the valve sleeve directly to the actuator. The sleeve is coupled to the actuator by a stiff relief spring. The spring-coupled sleeve and actuator body move together (float) under normal conditions. The relief spring compresses to accommodate excess actuator piston travel in over-temperature conditions, preventing possible damage to the valve.
A further aspect of the present invention relates to the flexibility provided by the unique structure of the thermal flow control valve. The basic valve components may be configured as a two-way thermally responsive shut-off valve, a thermally responsive three-way valve or as a temperature-responsive mixing valve. Each of the embodiments has an axial flow path between an inlet and an outlet, allowing an xe2x80x9cin linexe2x80x9d installation.
The flow-through end cap rotates freely relative to the valve body to improve ease of installation and removal of the valve.